Derek Nalls wrote on Tue, Dec 15, 2015 04:43 PM UTC:
"Humans typically suffer more than computers from large branching
factors."
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Although the quoted remark is not generally untrue, I find generalizations
about the playing strength of humans at any particular game of little,
practical use because it varies radically between individuals.
A game with a high branching factor will (almost) certainly throw a dense,
cognitive fog around the tactical & strategic play of a novice, human
player [in the majority] yet an experienced, incisive human player [in the
minority] can usually see through this dense, cognitive fog to
consistently, correctly identify the most important offensive and/or
defensive move on the board and execute it. Humans are better than
computers at quick-and-accurate pattern recognition which is conducive to
being able to play many chess variants well. Computers use different,
non-geometric techniques to evaluate potential moves, anyway.
By contrast, I do not take exception to generalizations about the playing
strength of computers at any particular game because they are predictably,
reliably useful. The best available hardware running the best known
programming, customized to play a given game as well as possible, is the
given assumption.
A game with a high branching factor will certainly trap a computer player
within a search ply where it becomes intractible (i.e., unable to complete
it in less than a tremendous amount of time). All except the most trivial
chess variants with the lowest branching factors become intractible at some
point. Critically, it is a matter of how many plies can be completed
before this occurs (if very long time controls are allowed) and whether or
not this average number of completed plies represents a formidable AI
opponent to an intelligent, competent human player. If not, there is a
serious problem which can only be overcome by heavy pruning within an
evaluation function.
Light to moderate pruning will not address the problem to a non-trivial
extent. Heavy pruning is risky. Any errors in the evaluation function are
potentially catastrophic and there are many places for such game-specific
errors to exist unknown. If an evaluation function occasionally throws
away from consideration a move(s) that needs to be made, then the human
player will likely soon discover tactics to routinely, successfully beat
his/her computer opponent every time.
